UMESH MULTITHREADING.ppt

A SEMINAR ON

MULTITHREADED PROGRAMMING USING

JAVA THREADSSUBMITTED TO:MISS.A.A.KUJURH.O.D. I.T. DEPT.I.G.E.C. SAGAR SUBMITTED BY-

UMESH KUMAR PRAJAPATI0601IT091055

V SEM. I.T.

GUIDED BY:MR RAJESH AHIRWARI.T. DEPT.

I.G.E.C. SAGAR

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CONTENTS

IntroductionThread ApplicationsDefining ThreadsJava Threads and States

Priorities

Advanced Issues:Concurrency Models: master/worker, pipeline, peer processingMultithreading Vs multiprocessing

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A single threaded program

class ABC

{

….public void main(..)

{

…

..

}

}

begin

body

end

4

A Multithreaded Program

Main Thread

Thread A Thread B Thread C

start startstart

Threads may switch or exchange data/results

5

ServerThreads

Server ProcessClient 1 Process

Client 2 Process

Multithreaded Server: For Serving Multiple Clients Concurrently

Internet

6

Web/Internet Applications:Serving Many Users Simultaneously

Internet Server

PC client

Local Area Network

PDA

7

Printing ThreadPrinting Thread

Editing Thread

Editing Thread

Modern Applications need Threads (ex1):Editing and Printing documents in background.

8

What are Threads?

A piece of code that run in concurrent with other threads.

Each thread is a statically ordered sequence of instructions.

Threads are being extensively used express concurrency on both single and multiprocessors machines.

Programming a task having multiple threads of control – Multithreading or Multithreaded Programming.

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Java Threads

Java has built in thread support for MultithreadingSynchronization Thread SchedulingInter-Thread Communication:

currentThread start setPriorityyield run getPrioritysleep stop suspendresume

Java Garbage Collector is a low-priority thread.

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1st method: Extending Thread class

Create a class by extending Thread class and override run() method: class MyThread extends Thread {

public void run() { // thread body of execution } }

Create a thread: MyThread thr1 = new MyThread();

Start Execution of threads: thr1.start();

Create and Execute: new MyThread().start();

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An example

class MyThread extends Thread { public void run() { System.out.println(" this thread is running ... "); }}

class ThreadEx1 { public static void main(String [] args ) {

MyThread t = new MyThread(); t.start();

}}

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2nd method: Threads by implementing Runnable interface

Create a class that implements the interface Runnable and override run() method:

class MyThread implements Runnable{ ..... public void run() { // thread body of execution }}

Creating Object: MyThread myObject = new MyThread();

Creating Thread Object: Thread thr1 = new Thread( myObject );

Start Execution: thr1.start();

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An example

class MyThread implements Runnable { public void run() { System.out.println(" this thread is running ... "); }}

class ThreadEx2 { public static void main(String [] args ) { Thread t = new Thread(new MyThread()); t.start(); } }

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Life Cycle of Threadnew

ready

start()

running

deadstop()

dispatch

completion

wait()

waitingsleeping blocked

notify()

sleep()

Block on I/O

I/O completed

Time expired/interrupted

suspend()

resume()

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Three threads example

class A extends Thread{ public void run() { for(int i=1;i<=5;i++) { System.out.println("\t From ThreadA: i= "+i); } System.out.println("Exit from A"); }}

class B extends Thread{ public void run() { for(int j=1;j<=5;j++) { System.out.println("\t From ThreadB: j= "+j); } System.out.println("Exit from B"); }}

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class C extends Thread{ public void run() { for(int k=1;k<=5;k++) { System.out.println("\t From ThreadC: k= "+k); }

System.out.println("Exit from C"); }}

class ThreadTest{ public static void main(String args[]) { new A().start(); new B().start(); new C().start(); }}

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Run 1

[raj@mundroo] threads [1:76] java ThreadTest From ThreadA: i= 1 From ThreadA: i= 2 From ThreadA: i= 3 From ThreadA: i= 4 From ThreadA: i= 5Exit from A From ThreadC: k= 1 From ThreadC: k= 2 From ThreadC: k= 3 From ThreadC: k= 4 From ThreadC: k= 5Exit from C From ThreadB: j= 1 From ThreadB: j= 2 From ThreadB: j= 3 From ThreadB: j= 4 From ThreadB: j= 5Exit from B

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Run2

[raj@mundroo] threads [1:77] java ThreadTest From ThreadA: i= 1 From ThreadA: i= 2 From ThreadA: i= 3 From ThreadA: i= 4 From ThreadA: i= 5 From ThreadC: k= 1 From ThreadC: k= 2 From ThreadC: k= 3 From ThreadC: k= 4 From ThreadC: k= 5Exit from C From ThreadB: j= 1 From ThreadB: j= 2 From ThreadB: j= 3 From ThreadB: j= 4 From ThreadB: j= 5Exit from BExit from A

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Process Parallelism

int add (int a, int b, int & result)

// function stuff

int sub(int a, int b, int & result)

// function stuff

pthread t1, t2;

pthread-create(&t1, add, a,b, & r1);

pthread-create(&t2, sub, c,d, & r2);

pthread-par (2, t1, t2);

pthread t1, t2;

pthread-create(&t1, add, a,b, & r1);

pthread-create(&t2, sub, c,d, & r2);

pthread-par (2, t1, t2);

MISD and MIMD Processing

abr1cdr2

abr1cdr2

addadd

subsub

Processor

Data

IS1

IS2

Processor

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do““

dn/2

dn2/+1

““dn

SortSort

Data

IS

Data Parallelism

sort( int *array, int count)

//......

//......

pthread-t, thread1, thread2;““pthread-create(& thread1, sort, array, N/2);pthread-create(& thread2, sort, array, N/2);pthread-par(2, thread1, thread2);

pthread-t, thread1, thread2;““pthread-create(& thread1, sort, array, N/2);pthread-create(& thread2, sort, array, N/2);pthread-par(2, thread1, thread2);

SIMD Processing

SortSort

Processor

Processor

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Thread Priority

In Java, each thread is assigned priority, which affects the order in which it is scheduled for running. The threads so far had same default priority (NORM_PRIORITY) and they are served using FCFS policy.

Java allows users to change priority:ThreadName.setPriority(intNumber)

– MIN_PRIORITY = 1

– NORM_PRIORITY=5

– MAX_PRIORITY=10

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Thread Priority Example

class A extends Thread{ public void run() { System.out.println("Thread A started"); for(int i=1;i<=4;i++) { System.out.println("\t From ThreadA: i= "+i); } System.out.println("Exit from A"); }}class B extends Thread{ public void run() { System.out.println("Thread B started"); for(int j=1;j<=4;j++) { System.out.println("\t From ThreadB: j= "+j); } System.out.println("Exit from B"); }}

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Thread Priority Example (Continue…)class C extends Thread{ public void run() { System.out.println("Thread C started"); for(int k=1;k<=4;k++) { System.out.println("\t From ThreadC: k= "+k); } System.out.println("Exit from C"); }}class ThreadPriority{ public static void main(String args[]) { A threadA=new A(); B threadB=new B(); C threadC=new C(); threadC.setPriority(Thread.MAX_PRIORITY); threadB.setPriority(threadA.getPriority()+1); threadA.setPriority(Thread.MIN_PRIORITY); System.out.println("Started Thread A"); threadA.start(); System.out.println("Started Thread B"); threadB.start(); System.out.println("Started Thread C"); threadC.start(); System.out.println("End of main thread"); }}

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Online Bank: Serving Many Customers and Operations

Internet Bank Server

PC client

Local Area Network

PDABank

Database

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ServerThreads

Message PassingFacility

Server ProcessClient Process

Client Process

User Mode

Kernel Mode

Multithreaded Server

Multithreaded Server

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A Multithreaded Program

MathThreads

MathSin MathCos MathTan

start start start

MathThreads

join join join

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Thread Programming models

Thread concurrency/operation models

The master/worker model

The peer model

A thread pipeline

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taskXtaskX

taskYtaskY

taskZtaskZ

main ( )main ( )

WorkersProgram

Files

Resources

Databases

Disks

SpecialDevices

Master

Input (Stream)

The master/worker model

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The peer model

taskXtaskX

taskYtaskY

WorkersProgram

Files

Resources

Databases

Disks

SpecialDevices

taskZtaskZ

InputInput

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Resources Files

Databases

Disks

Special Devices

Files

Databases

Disks

Special Devices

Files

Databases

Disks

Special Devices

Stage 1Stage 1 Stage 2Stage 2 Stage 3Stage 3

Program Filter Threads

Input (Stream)

A THREAD PIPELINE

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Process Parallelism Process Parallelism Process Parallelism Process Parallelism

P1P1

P2P2

P3P3

time

time

No of execution processes <= the number of CPUs

No of execution processes <= the number of CPUs

CPU

CPU

CPU

Multithreading - Multiprocessors

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Multithreading on Uni-processor

Concurrency Vs Parallelism Process ConcurrencyProcess Concurrency Process ConcurrencyProcess Concurrency

Number of Simultaneous execution units > number of CPUs

Number of Simultaneous execution units > number of CPUs

P1P1

P2P2

P3P3

time

time

CPU

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Application

Application Application

Application

CPU

Better Response Times in Multiple Application Environments

Higher Throughput for Parallelizeable Applications

CPU

CPU

CPU CPU CPU

Threaded Libraries, Multi-threaded I/OThreaded Libraries, Multi-threaded I/O

Multi-Processing (clusters & grids) and Multi-Threaded Computing